Modelling The Short-Circuit Reliability Of Ageing Power Transformers

The short-circuit reliability of ageing transformers is assessed based on an existing reliability model taken from literature. The model of interest investigates the reliability of insulation wear due to a combination of insulation ageing and mechanical stress caused by short-circuits. The model is adapted for use with modern transformer loading criteria and is also adapted to allow for greater applicability in reliability assessments. The results indicate that aged transformers present an increased risk of failure when exposed to a short-circuit of sufficient magnitude and also that the insulation wear failure mode will precede the insulation end-of-life when transformers are exposed to repeated short-circuits across their operational life.